Contradirectional waveguide coupler



Feb. 11, 196 9 ;.s. DAGL-IAN ETAL- 3,427,570

CONTRADIREC 'I' IONAL WAVEGUIDE COUPLER Filed June 14, 1967 John S.Duglidn John W. Grace Carl R Clasen INVENTORS.

United States Patent O 3,427,570 CONTRADIRECTIONAL WAVEGUIDE COUPLERJohn S. Daglian, North Wales, Pa., John W. Grace, Las

Vegas, Nev., and Carl P. Clasen, Cherry Hill, N.J., assignors, by mesneassignments, to the United States of America, as represented by theSecretary of the Army Filed June 14, 1967, Ser. No. 646,125 U.S. Cl.333-10 Int. Cl. H01p /14 4 Claims ABSTRACT OF THE DISCLOSURE BACKGROUNDOF THE INVENTION I This invention is in the field of high-frequencydirectional energy couplers, in particular a coupler for use between twomicrowave guides.

Many types of high-frequency directional waveguide couplers are known. Aspecific example of one such known coupler is that shown by S. Sensiperin U.S. Patent No. 2,641,648, issued June 9, 1953. This patent discussesvarious types of known couplers, such as the Bethe hole coupler, whereinboth electric and magnetic coupling takes place through a single hole ina common wall between two waveguides. The Sensiper invention is anarrangement using separate couplers for electric and magnetic fields,with the couplers being in a common wall between two waveguides. Theelectric coupling is accomplished by a probe, and the magnetic coupling,by a slot. The probe is supported by an insulator in the common wall.

SUMMARY OF THE INVENTION This invention is a directional coupler betweentwo parallel rectangular waveguides having a common broad wall with atransverse slot in the common wall. The slot has an enlarged centerportion, through which a post extends. One end of the post is fixed to anon-common broad wall on one of the waveguides, and extends into theother waveguide. This arrangement makes for a simpler physicalconstruction than the above patent arrangement, and will be more rugged,since no insulator is used. Also, no dielectric losses from an insulatorexist. The invention realizes a broad bandwidth and a high directivity,compared to the known couplers.

An object of this invention is to provide a novel contradirectionalwaveguide coupler.

Another object is to provide a contradirectional coupler which issimpler, cheaper and more rugged than known couplers.

Yet another object is to provide a waveguide coupler using aperforation-post combination.

These, and other objects which may be obvious to one skilled in the artmay be realized from the invention as descrbied herein.

Patented Feb. 11, 1969 BRIEF DESCRIPTION OF THE DRAWING The singledrawing figure shows a pictorial view of the inventive coupler, with asection cut away.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention may be bestunderstood by reference to the drawing, which shows two parallelrectangular waveguides generally designated 1 and 2. These waveguideshave a common broad wall 3, and respective noncommon broad walls 4 and5. The cut-away portion reveals a perforation generally designated 6 inwall 3. Perforation 6 is composed of a slot portion 6a and a centralenlarged portion 6b. A post 7 is perpendicularly attached to wall 4, andpenetrates perforation 6 through enlarged portion 6b. Post 7 extendsinto waveguide 2, but does not touch broad wall 5. Both post 7 andperforation 6 are centered on respective centerlines of walls 4 and 3,and perforation 6 is perpendicular to the centerline of wall 3. Arrow 8in waveguide 2 shows the direction of the main transmission path ofenergy. Arrow 9 in waveguide 1 shows the direction of the coupledenergy, with arrow 10 showing the direction of waste energy from thecoupler. The diameter of post 7 is elected to optimize the directivityand impedance match of the coupler.

The length of post 7 and the length of slot 6a provides two wellcontrolled variables that determine the exact design desired. Enlargedportion 6b may also be varied for specific conditions. Post 7 may bethreaded in a tapped hole in wall 4, to allow ready adjustment of itspenetration into perforation 6. Post 7 provides electric coupling forenergy from waveguide 2 into waveguide 1, and slot 6 provides magneticcoupling. The waste power in direction 10 is optimized at a minimumvalue and may be absorbed by a matched waveguide load (not shown). Theperforation-post combination does introduce some fringing of theelectric and magnetic coupling, but proper selection of parametersminimizes the effects, and a contradirectional coupler is produced thatfeatures high directivity with a good voltage standing wave ratio(VSWR), relatively flat coupling (over the design frequency band), andconsistent phase characteristics.

An example of the particular coupler in accord with the invention is asfollows. For a 10% bandwith (:L-S%) about 5.55 gHz, with at least 15 dbdirectivity over the band, the following coupler dimensions may be used(all dimensions in inches).

These dimensions allow a maximum VSWR of 1.12 in the band from 5.3 to5.8 gHz. The directivities and couplings at various frequencies aregiven below (in db).

Frequency (gHz.) Coupling Directivity The desired result is obviouslyobtained. The above dimensions are intended not to be limiting in anyway, but are for particular frequencies and particular waveguides. Manyother combinations of post length, post diameter, slot length, etc., maybe used.

We claim:

1. A microwave coupler comprising a first section of rectangularwaveguide parallel to a second section of rectangular waveguide, with acommon broad wall therebetween; said wall having a transverse slot witha central enlarged portion; a post fixed to a non-common broad wall ofsaid first section of waveguide, and extending through said enlargedportion of said slot.

2. The coupler of claim 1 wherein said slot is generally rectangular inshape.

3. The coupler of claim 1 wherein said post is of a circularcross-section.

4. The coupler of claim 3 wherein said enlarged portion is round.

References Cited UNITED STATES PATENTS ELI LIEBERMAN, Primary Examiner.

10 PAUL L. GENSLER, Assistant Examiner.

US. Cl. X.R.

